Solid ink jet printers were first offered commercially in the mid-1980's. One of the first such printers was offered by Howtek Inc. and used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings that fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends with separate rounded, five, six, and seven sided shapes each corresponding to a particular color.
Later more successful solid ink printers, such as the Tektronix Phaser.RTM. III and the Jolt printer offered by Dataproducts Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed chute and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. As phase change ink color printers increase their printing speed there is the need to provide larger sized ink sticks so that refill of the ink reservoir in the print head is less frequent and more output or prints can be produced between refills. Also, as the number of phase change ink printers increase it is desirable to use different shaped ink sticks with each model of printer that employs different ink formulations to minimize the potential for the inadvertent use of the incorrect ink in a particular printer since the inks and the printers are customized and made for each to optimize printer output. Current ink sticks employ shapes that have two mirror planes of symmetry.
Also, in printer designs where there is not a steep or generally vertical feed path to the heater plate, some provisions must be made to prevent the solid masses of shaped ink from sticking to the sides of the feed chutes so that regardless of the ink stick shapes employed an unrestricted feed of ink sticks proceeds down into the heater plate for melting. The melted ink then fills the individual colored ink reservoirs that are usually located within the print head. Larger sized ink sticks especially have the tendency to hang up or catch within the feed chutes when there is not a steep feed path to the melt plate, especially because of the sticky nature of the ink sticks' waxy exterior surfaces.
This problem is solved in the design of the ink stick masses of the present invention by the use of a drafted or tapered chiral design that presents only a small surface area for the ink stick to contact the adjacent wall of the feed chute. The opposing sides of the ink sticks extend between the top and the bottom surfaces at an angle.